Fans typically are the low cost, but essential element in electronic systems which generate heat and require cooling. Failure of a fan system will lead to excessive heat generation and possible failure and/or damage to the electronic systems.
Sensors have been employed to detect the failure of the fan motor of DC electric motors by detecting the absence of current pulses in the input drive signal, and tachometers have been employed to detect the rotation of fans. Detection of fan failure alone does not indicate whether the air flow may be blocked by venturi blockage, because the fan blades can still be rotating even when the venturi area is completely blocked. Electro-mechanical sensors have been employed to detect air flow in the system, but are susceptible to mechanical malfunctions. Thermal detectors have been used to detect high ambient temperature of the electronic systems, but do not differentiate the cause of a high temperature. Such detectors provide detection of overheating so that an alarm may be activated so that some action may be taken before any damages including loss of data and/or fire arise. Thermal detectors are an expensive approach and require extensive testing to determine the trip point.